The Danube Bulgars, a Turkic tribe, had conquered the Slavs immediately south of the Danube, absorbing a large portion of ancient Dacia in 676.

The Bulgars, who will soon be permeated by Vlach and, even more thoroughly, by Slavic elements, will unite with the Slavs to oppose Imperial control.

At the same time, their conquests will carry them deeper into the ambit of Constantinopolitan Christianity.

The Bulgarian khan Asparukh, eluding Constantine IV's attempts to defeat him, has by 681 forced the emperor to recognize the first Bulgarian state, which, with its capital at Pliska (near modern Shumen), combines a Bulgarian political structure with Slavic linguistic and cultural institutions.

Occupying lands south of the Danube into the Thracian plain—much to the humiliation of Constantinople—the Bulgars have thus deprived the empire of control in the north and central Balkans.